Winter sowing is an easy way to start seeds outside during the winter. Seeds are sown in miniature greenhouses made from recycled plastic containers, and then put outside in the snow and freezing cold. The rest of the work is left to Mother Nature. Once the weather starts to warm in the spring, the seeds will germinate at their own pace, just as in nature.
Since the winter sown containers go outside, they don’t take up space in the house. With winter sowing, there’s no need to sterilize seedling flats and trays, you don’t need any special equipment (like lights or heat mats), there’s no risk of the seedlings damping off, and no need to harden them off. Plus, winter sown seedlings are hardier and more robust than seeds sown indoors, which means they have a much higher survival rate.
How To Winter Sow Seeds:
- Choose the winter sowing containers - Winter sowing containers can be made out of items you throw out every day; containers like milk jugs, 2 liter bottles, restaurant/deli/bakery food containers, ice cream buckets…etc. The shape and size of the container doesn’t matter, but it must be made of transparent plastic, deep enough to allow for 2-3 inches of soil in the bottom, and tall enough to allow a few inches of headspace for the seedlings to grow. See my posts Containers for Winter Sowing Seeds or More Containers for Winter Sowing Seeds for more information.
|Winter sowing container options|
- Prepare the containers – To prepare the containers for winter sowing seeds, you will first want to clean the containers. If you’re using a tall narrow container like a 2 ltr bottle or milk jug, you’ll need to cut the container in half as well. Next, poke holes in the top and bottom of the container. Heating a knife and melting the holes makes this task easier (use an old knife because it will turn black over time and have plastic residue on it), otherwise you can use a drill or something sharp to poke the holes. Poke enough holes in the bottom of the container to allow the water to drain so the seeds won’t drown. Add the same amount of holes in the top of the container (if you use milk jugs or 2 ltr bottles, simply leave the caps off rather than poking holes). The holes in the top are there to vent the containers so they won’t overheat, and also to allow rain and moisture to enter the containers.
|How to prepare winter sowing containers|
- Add soil to the container - Regular potting soil can be used for winter sowing seeds. I’ve also used the seed starting soil mix that is specifically made for starting seeds, but it’s a little more expensive. Just make sure you don’t go super cheap on the potting soil. Cheap dirt is too heavy and the seeds will have a hard time germinating, or may end up rotting. Always use fresh, sterile soil when starting seeds; and never, never use soil from your garden in any of your winter sowing containers.
- Sow the seeds – The best types of seeds to use for winter sowing are the seeds of cold hardy annuals, herbs and vegetables, or plants that are perennial in your zone. If you’re unsure, check the seed packet. Look for terms like “self sowing”, “direct sow outside in the fall”, “direct sow outside in early spring” or “cold stratification”… keywords like these are good indicators of seeds that will work well for winter sowing. The number of seeds you add to each container is up to you, but I prefer to space them out a bit to make it easier to separate the seedlings for planting.
|Winter sowing seeds|
- Label the containers – There are a few ways you could label winter sowing containers. Some people use masking or duct tape to label their containers, and others write directly on the top of the container. However, if you use pencil or a permanent marker, the writing will eventually fade in the sun. Some people swear that paint pens won’t fade, but I haven’t tested this out yet. If you choose to use tape, put it on the bottom of the container so it won’t fade. My preferred method for labeling winter sowing containers is to use cut up old vinyl mini blinds and write on them with pencil. I push the marker into the soil, and have never had one of them fade. You could also reuse plant markers from bedding plants if you save those.
- Water the containers – Wet down the potting soil in the winter sown containers thoroughly, and allow them to drain. I give mine a light shower with the sprayer in my kitchen sink because it won’t disrupt the soil. If the soil is really dry, water the container a few times to make sure the soil becomes moist.
- Put the lids on – Putting the lids on your winter sowing containers depends on what type of container you use. If the lid snaps on and fits tight, then you’re done. If you used a tall container that you cut in half (i.e.: milk jug, 2ltr bottle), then you can use tape to attach the lid back onto the container (but leave the caps off). You can tape the lids on any container if the lid doesn’t fit tightly, just make sure you don’t completely cover the transparent parts.
|Watering the winter sowing containers|
- Put the container outside – Move your winter sown container outside in a spot where they are protected from heavy wind, but will get enough moisture and full sun. If you have pets or children, put the winter sown containers on a table or other spot where they will be out of reach.
- Forget about them – Once the winter sown seed containers are moved outside, you can pretty much forget about them until early spring. Don’t worry, it’s even ok if they’re covered by snow for a few months.
|Winter sown seed containers under snow|
Once the weather starts to warm up, check your winter sown containers regularly for any signs of growth. Cold weather plants will start to germinate first, things like broccoli, lettuce, spinach and spring blooming perennials.
The only maintenance you have to do at this point is to make sure they don’t overheat, and make sure the soil doesn’t dry out. Once the seedlings get tall enough where they are touching the top of the inside of the container, it’s time to remove the lids. Winter sown seedlings can dry out pretty quickly once you take the lids off, so check them at least once a day and water if necessary. Once the lids are off, keep an eye on the weather report. If there is a chance of frost, cover the containers with a sheet or blanket overnight.
|Winter sown seedlings ready to plant|
More reading about winter sowing seeds:
Winter Sowing Q&A – Getting Started
Winter Sowing Q&A – Winter Maintenance
Winter Sowing Q&A – Early Spring
Winter Sowing FAQ – Spring
Containers for Winter Sowing Seeds
More Containers for Winter Sowing Seeds
Winter Sowing During a Mild Winter
Cleaning Winter Sowing Containers